Israeli authorities' decision to lift a gag order has revealed the extent of serious spying charges brought against a journalist from the country who is accused of leaking top secret military documents.

Anat Kam, 23, has been under house arrest since December and is due to go on trial next week. The indictment accuses her of copying more than 2,000 classified military documents while she did her national service as a clerk in the office of a top Israeli general who was head of the military's central command with responsibility for the occupied West Bank.

As many as 700 of the documents were marked top secret, Israel alleges. Kam, who became a journalist after her national service, is accused of passing them to Uri Blau, a Ha'aretz newspaper reporter. Blau is now living in London, apparently due to concerns he might face prosecution. Kam is accused of earlier trying to pass them to another reporter who refused to take them and is listed now as a prosecution witness.

Blau wrote a prominent investigation in Ha'aretz about the Israeli military's assassination policy in November 2008. He reported that the military had been assassinating Palestinian militants in the West Bank in direct contravention of an Israeli high court ruling that said efforts should be made to arrest them first.

The Ha'aretz piece was accompanied by copies of military documents but it was approved by the Israeli military censor before publication. A year after the article Kam was arrested.

Kam's lawyer told reporters she had not compromised Israel's security. "At no stage of this affair was Israel's security damaged. Certainly, there was no intent to do so," Eytan Lehman said. "If she posed a threat to national security, she would not have been allowed to stay home and continue working."

Dov Alfon, the editor of Haaretz, told the Guardian last week that Blau would stay in London "as long as needed".